While casting provides the products you need, sometimes secondary machining activities are required in order to get the polyurethane elements into just the right place and in the right working order. Hard urethanes (90 Shore A and up) are fairly easy to machine.
The key is to rely on a plastics expert who understands the machinability of urethanes and has the tools to do so. Here are a few basics to keep in mind:
- Band saws do a great job due to longer blades which stay cooler. A 10 tooth-per-inch blade will give a finer finish.
- Lathe, facing and boring are possible with speed and shape of tools dependent on the hardness of the urethane.
- Knifing can be done, but the tool must be razor sharp and as thin as possible.
- Milling is best at a feed rate of 15 to 20 inches per minute.
- Slow spiral drills are the best for drilling to minimize binding and heat.
- Grinding is best accomplished with fine grain, medium harness, coarse texture carborundum grinding wheels.